In critically ill preterm and term infants with cardiovascular compromise, oxygen delivery fails to meet the demand of cellular oxygen consumption, and unless recognized early and treated aggressively, failure of the circulatory system is associated with increased mortality or potentially severe short/long-term morbidity [1]. There has been considerable progress in our understanding of developmental cardiovascular physiology, however there remains significant gaps in our knowledge particularly pertaining to treatment of patent ductus arteriosus (PDA).